Evaluating the safety profile of calcineurin inhibitors: cancer risk in patients with systemic lupus erythematosus from the LUNA registry—a historical cohort study

Background Previous studies have shown conflicting evidence regarding the incidence of cancer in patients with systemic lupus erythematosus (SLE) compared with that in healthy individuals. Calcineurin inhibitors (CNIs) such as cyclosporine and tacrolimus have been widely used to treat SLE; however, their effects on cancer risk remain unclear. We aimed to investigate the incidence of cancer in patients with SLE and determine the potential association between CNI use and cancer risk. Methods The standardized incidence ratio (SIR) of cancer among patients with lupus in the Lupus Registry of Nationwide Institutions (LUNA) was calculated based on the age-standardized incidence rate of cancer reported by Japan’s Ministry of Health, Labour and Welfare. We also examined the association between CNI exposure and cancer risk, while considering potential confounding factors. The analysis accounted for confounding variables such as age, sex, smoking history, maximum glucocorticoid dose, treatment history with cyclophosphamide, ongoing hydroxychloroquine, Systemic Lupus International Collaboration Clinics/American College of Rheumatology Damage Index (SDI) value (excluding cancer occurrence), comorbidity of diabetes mellitus, and smoking history. Results The study included 704 patients with SLE (625 females; 88.8%) with a median age of 44 years [interquartile range (IQR) = 34–55] years. The median past maximum glucocorticoid dose was 40 mg/day [IQR = 30–60 mg/day], and the SDI at registration was 1 [IQR = 0–2]. Among the patients, 246 (35.1%) had smoking histories, and 38 (5.4%) experienced cancer complications. Gynecological malignancies accounted for 63.2% of all cancers. The SIR of cancer in the LUNA cohort was 1.08 (95% confidence interval [CI] = 0.74–1.43). No statistically significant risks of cancer were found in relation to CNI treatment history; the odds ratio using multiple logistic regression was 1.12 (95% CI = 0.42–3.00), the risk ratio using standardization was 1.18 (95% CI = 0.47–2.16), and the risk ratio using inverse probability weighting was 1.8 (95% CI = 0.41–4.66). Conclusions The incidence of cancer in patients with SLE in the LUNA cohort did not significantly differ from that in the general population. These findings suggest that CNI treatment in this cohort did not pose a risk factor for cancer development. Supplementary Information The online version contains supplementary material available at 10.1186/s13075-024-03285-x.


Background
Systemic lupus erythematosus (SLE) and other autoimmune diseases are associated with an increased risk of certain types of cancers, although the results are inconsistent [1,2].Several extensive SLE cohort studies and meta-analyses have suggested that the rate at which patients with SLE are diagnosed with cancer is 14-76% higher than that in the general population [3].In particular, patients with SLE may be at an increased risk for other cancers, such as lung, liver, cervical, and hematologic cancers, including non-Hodgkin lymphoma, Hodgkin lymphoma, and leukemia [4][5][6][7].Many studies on putative risk factors for malignancies in this population have been conducted in response to the distinct cancer risk profiles of patients with SLE.Immunosuppressive medications, SLE disease activity, immunological abnormalities, viral and hormone exposure, autoantibodies, genetics, and many other variables increase the risk of malignancies in these patients [3].
Treatment with immunosuppressive or cytotoxic agents, such as hydroxychloroquine (HCQ), azathioprine, cyclophosphamide (CYC), methotrexate (MTX), and mycophenolate mofetil (MMF), is often combined with systemic glucocorticoids in patients with refractory symptoms or major organ involvement [8].CYC is known to increase the risk of cancer associated with SLE, while HCQ decreases it [9].Calcineurin inhibitors (CNIs), such as cyclosporine (CsA) and tacrolimus (TAC), have been postulated as potential treatment strategies for SLE and lupus nephritis (LN) because of the ability of these drugs to reduce T cell activation and promote immunosuppression [10].In contrast, the chronic use of CsA and TAC has been reported to increase cancer incidence in patients who have received solid organ transplants [11].Previous studies have indicated that CNIs can affect DNA repair mechanisms and promote angiogenesis and the invasion of non-metastatic cells in vitro [12,13].Despite advances in our knowledge of the processes that affect cancer risk in patients with SLE, the relationship between CNIs and cancer onset remains unclear.
In the present study, we calculated the standardized incidence ratio (SIR) of cancer among patients with lupus in the Lupus Registry of Nationwide Institutions (LUNA) based on the age-standardized incidence rate of cancer reported by Japan's Ministry of Health, Labour and Welfare.We also investigated whether CNIs are associated with an increased risk of developing cancer.

Patients and methods
This historical cohort study used a cohort from the LUNA, in which 10 Japanese institutions participated.This registry was established in 2016 to examine the associations among clinical presentation, serological testing, socioeconomic background, and outcomes in patients with SLE.The LUNA registry contains data on patients aged 20 years and older diagnosed with SLE using the 1997 American College of Rheumatology (ACR) criteria [14].Approximately 900 cases (1.5%) of patients with SLE in Japan have been reported in LUNA.
All patients participating in the LUNA registry provided written informed consent, and the opt-out strategy was chosen for individual studies.Patients who refused to provide informed consent were excluded.
This study was performed in accordance with the Declaration of Helsinki and approved by the Investigation and Ethics Committee of Nagasaki University Hospital (approval nos.18061802 and 20021020).Informed consent was obtained from all participants before enrollment in the study, and patient information was anonymized and de-identified before analysis.

Data collection
This study used information from electronic medical records from February 2016 to September 2019.The data included laboratory tests, medications, activity scores, and comorbidities.We used identical methods to collect data on cancer development from the past to the time of the last observation using self-administered questionnaires completed by registered patients.Data were collected annually until the patient died, was discharged from the hospital, or consented to withdrawal from the registry.Demographic data included age at enrollment to the LUNA registry; age at diagnosis of SLE; sex; SLE Disease Activity Index 2000 (SLEDAI-2 K) [15]; The Systemic Lupus International Collaborating Clinics/ACR Damage Index (SDI) [16] (excluding the occurrence of cancer); comorbidities of LN, diabetes mellitus (DM), hypertension (HT), and hyperlipidemia (HL); habitual drinking; smoking history; cervical cancer vaccination history; maximum glucocorticoid dose (mg/day); and the use of immunosuppressant treatment.

Exposure
Exposure was defined as continuous CNI (CsA and TAC) use from the time of SLE diagnosis to the time of study registration.Patients with cancer that developed before CNI treatment or those whose onset date was unknown were excluded.

Study objective and outcome measures
The objective was to assess the safety of CNIs in patients with SLE with the primary outcome being the incidence of malignancies in these patients.This was evaluated by tracking the occurrence of various cancers (excluding cervical dysplasia) from the initiation of CNI therapy until the time of LUNA registration.

Potential confounders
The following nine variables were identified as potential confounders based on findings from a previous study [1] and the clinical standpoint of the rheumatologist: (1) age at enrollment in the LUNA registry, (2) age at the time of diagnosis, (3) sex, (4) maximum glucocorticoid dose, (5) CYC treatment history, (6) ongoing HCQ, (7) SDI value (excluding the occurrence of cancer), ( 8) DM comorbidity, and ( 9) smoking history.All potential confounders were assessed and documented at registration.Items (4), ( 5), (8), and (9) included events from SLE onset until the time of registration; items (1), ( 2), (4), and (7) were continuous variables; and the remaining items were binary variables.A design diagram is shown to clarify the key points of each item (Additional file 1: Figure S1).

Statistical analyses
First, the background characteristics of the LUNA cohort with and without cancer were summarized and compared using Wilcoxon's rank sum and Fisher's exact tests.Second, we calculated the SIR of cancer among patients with SLE based on the age-standardized incidence rate of cancer in 2016 as reported by the Cancer Statistics, Cancer Information Service, National Cancer Center, Japan National Cancer Registry, and Ministry of Health, Labour and Welfare.Third, we evaluated whether the history of CNI treatment was associated with cancer risk.Relative risk was estimated using crude analysis, a multivariable logistic regression model, standardization using propensity scores (PSs), and inverse probability weighting (IPW) to account for confounders [17].Multiple imputations were used because data were missing.There were 100 imputed datasets, and the estimates from each dataset were combined using Rubin's rules.For standardization and IPW using PSs, the PSs were first calculated for the 100 imputed datasets.Adjusted estimates were then calculated for each dataset and finally combined [18].The 95% confidence intervals (CIs) were derived using the bootstrap method with 1000 iterations.See the Additional file 2 for details of the analysis method.
All statistical analyses were performed using JMP ® Pro16 (SAS Institute, Cary, NC, USA) and R Statistical Software (Foundation for Statistical Computing, Vienna, Austria).A p-value was considered statistically significant when it was less than 0.05 (two-tailed) or when the 95% confidence interval did not include the null value.

Patient characteristics in the study
Of the 929 enrolled patients, 704 were followed up for the occurrence of cancer (Fig. 1).Thirty-eight cancer cases (5.4%), excluding cervical dysplasia, were identified within a median of 14 years from SLE onset to registration (Table 1).Patients with cancer were significantly older and had higher SDI scores (without cancer) at registration than those without cancer.In addition, a higher percentage of patients with cancer had DM and a history of smoking.

The SIR of cancer among patients with SLE
The SIR of cancer among patients with SLE was calculated based on the age-adjusted incidence of malignancies for each age group (Ministry of Health, Labour and Welfare, 2016) (Table 2).The SIRs of overall malignancies in total and in female patients with SLE compared with the general population were 1.08 (95% confidence interval [CI] = 0.74-1.43)and 1.18 (95% CI = 0.81-1.56),respectively.The incidence of malignancies in the LUNA cohort did not differ from that in the general population.

Crude risk difference and risk ratio of cancer development
Next, we examined the crude difference and risk ratio for developing cancer with and without CNI use (Table 3).Six patients (6.6%) in the CNI group and 32 patients (5.2%) in the non-CNI group developed cancer.The crude risk difference was 1.37 (95% CI = − 4.02 to 6.77), and the risk ratio was 1.26 (95% CI = 0.54-2.94).The risk of developing cancer with CNI use in the LUNA cohort was not significantly different from that without CNI use.

Adjusted odds/risk ratios and risk differences between CNI and non-CNI users
We then examined the odds/risk ratios and differences between CNI and non-CNI users after adjusting for potential confounders in the logistic regression analysis model, standardization, and IPW (Table 4).The odds ratio with the logistic model was 1.12 (95% CI = 0.42-3.00), the risk difference with standardization was 0.01 (95% CI = − 0.04 to 0.06), the risk difference with IPW was 0.05 (95% CI = − 0.04 to 0.24), the risk ratio with standardization was 1.18 (95% CI = 0.47-2.16),and the risk ratio with IPW was 1.8 (95% CI = 0.41-4.66).Even after adjusting for the confounders, the risk of developing cancer with CNIs did not differ significantly from that without CNIs in this study.

Discussion
Previous studies have shown conflicting evidence regarding the incidence of cancer in patients with SLE compared with that in healthy individuals.CNIs such as CsA and TAC have been widely used to treat SLE; however, their effects on cancer risk remain unclear.We aimed to investigate the incidence of cancer among patients with SLE in the LUNA cohort and the possible association between CNI treatment and cancer development.We found that the incidence of cancer in patients with SLE in the LUNA cohort did not significantly differ from that in the general population.Furthermore, our results suggest that CNI treatment in the LUNA cohort does not significantly increase the risk of cancer development.However, we recognize the importance of cautious interpretation and the need for further studies to confirm these findings in broader contexts.
Our first finding revealed that the incidence of cancer in patients with SLE in the LUNA cohort did not differ from that in the general population.There are conflicting views on whether SLE increases cancer risk.Some studies have suggested that patients with SLE may experience an elevated risk of certain types of cancer, such as lymphoma and cancer of the cervix [5].However, other sources suggest that having SLE does not significantly increase the risk of common cancers such as breast, uterine, ovarian, pancreatic, colon, and brain cancers and that the overall increased cancer risk is minimal [1,2,19].One study found that patients with SLE have a decreased risk of certain cancers, such as prostate and cutaneous melanoma [20].In our study, there was a high incidence of cancer in the cervical region (26.3%),breast (15.8%), and uterus (15.8%) in the LUNA cohort.However, the risk of cancer in individual organs was not examined owing to the limited patient numbers and is a subject of future investigation.Overall, our study provides evidence that patients with SLE in the LUNA cohort do not develop cancer more often than the general population.
The second finding suggests that CNI treatment is unlikely to be a risk factor for cancer development.To date, no association has been demonstrated between oral CNIs and cancer development in patients with SLE.Previous studies have shown that the immunosuppressive effects of CNIs contribute to tumor development by decreasing cancer cell surveillance.Additionally, there is evidence of direct tumor induction by CNIs [21][22][23].Skin cancer is associated with the use of CNIs in solid-organ transplantation [21].This may result from the localized inhibition of DNA repair and apoptosis in the skin.
Alternatively, recent findings have shown with moderate certainty that topical CNIs do not increase the risk of cancer in patients with atopic dermatitis [24].These findings support the safe use of topical CNIs for the optimal treatment of patients with atopic dermatitis.Furthermore, evidence indicates that medications including aspirin [25], nonsteroidal anti-inflammatory drugs [26], and glucocorticoids [27] may influence the risk of malignancy in SLE, although the data are mixed with some studies indicating a potential reduction in risk.Oral CNIs may modify the effects of these agents; however, our results may not indicate a direct effect of CNIs.
Our study makes a valuable contribution to the ongoing discussion regarding the safety of CNI treatment in patients with SLE.Our findings from the LUNA cohort indicate that patients with SLE do not exhibit a higher frequency of cancer development than the general population.Furthermore, our analysis suggests the lack of a strong association between CNI treatment and increased cancer risk in this specific cohort.This observation, while preliminary, may offer some reassurance to clinicians and patients about the use of CNIs in managing SLE and other autoimmune diseases.However, we emphasize the importance of further research to substantiate these findings and fully understand their clinical implications.
Our study has some limitations that should be considered.First, we analyzed only the LUNA cohort, which comprised patients from one geographical region, and our findings may not apply to other populations.Second, we could not evaluate the effects of the duration and dose of CNI treatment on the risk of cancer owing to the limited data.Therefore, the actual CNI exposure in patients may vary widely, and it may not be comparable between patients with cancer and cancerfree cases.Third, there is no established median period for the effects of CNI use on cancer development.Cancer that developed shortly after CNI initiation may not be linked to CNI.A sufficiently long follow-up period seems necessary to link cancer incidence and other outcomes in patients receiving CNI.Fourth, we could not investigate the potential effect of disease severity on the incidence of cancer in patients with SLE.Fifth, the LUNA cohort used HCQ less frequently (less than 30%), which may have led to a higher cancer incidence.Sixth, our results may have been altered by the many adjustment variables for cancer incidence outcomes.Finally, our study did not include other risk factors for cancer, such as other medications, food preferences, infectious diseases, obesity, and family history of cancer.These limitations may be overcome in the future as more patients are added through international collaborative studies involving SLE cohorts.Despite these limitations, our study has several strengths.First, we analyzed a large cohort of patients with SLE over a long follow-up period.Second, we used robust statistical methods to control confounding factors.

Conclusions
In conclusion, our study provides preliminary evidence that the incidence of cancer in SLE patients within the LUNA cohort may not differ significantly from that in the general population.Furthermore, our data suggest that CNI treatment is not a substantial risk factor for cancer development in this cohort.While these observations could be informative for clinicians treating SLE patients with CNIs, we emphasize the need for further research to confirm these findings and fully understand their implications.

Table 2
Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) of cancers in patients with systemic lupus erythematosus (SLE), total and females

Table 3
Crude risk difference and risk ratio of cancer development by calcineurin inhibitor useCNIs calcineurin inhibitors, CI confidence interval

Table 4
Adjusted odds/risk ratios and risk differences between CNI users and non-CNI users after adjustments for the logistic regression analysis, propensity scoring, and IPW CNI calcineurin inhibitor, IPW inverse probability weighting, CI confidence interval